It does not draw at all, if I render a scene or clear the screen then I simply get whatever is there.

Thanks for the link, I did read that part of the AllegroGL docs but was hoping that by calling allegro_gl_set_allegro_mode() I could just use good old Allegro routines. The program's behavious and comments here suggest that this will never work without the internal flipping.

Natuarlly the way to get this working is to process a file select dialog manually using algl_do_dialog. Amazingly I have little experience with the Allegro GUI as I tend to write my own (apart from the file selector as it is quite complex). I have already created a pretty comprehensive GUI for my OpenGL map editor which includes icon toolbars and drop down menus etc (using an orthoscopic matrix).

Well I will hunt around for an example of algl_do_dialog (exdialog.c), hopefully I can still use the Allegro file select dialog with this function.